2.2. Inoculum
The inoculum was taken from the AD plant of Wykey Farm. This
was fed on 20% CM, 70% MS and 10% triticale at a loading rate of 18
tonnes day1, and at the time of sampling had been operating for
8 months. During this time the ammonia concentration had risen
and the digester had experienced some operational difficulties,
with methane concentration in the biogas falling to 41%. A series
of remedial measures were undertaken in an attempt to acclimate
the digester to ammonia. These included reducing the operating
temperature from 41 C to 37 C, increasing the recirculation rate
of separated liquor, and the addition of trace elements. The inoculum
taken was methanogenically active despite a history of
stressed conditions, and showed some evidence of partial acclimatisation
to high ammonia concentrations. After being transported to the laboratory, the inoculum was sieved and maintained at 36 C
for 3 days before being fed.